The present invention relates to emulsions which remain perfectly stable over time, prepared from an emulsifier comprising at least one polyglycoside and at least one fatty alcohol, a process for stabilising the emulsions and an emulsifying agent.
Emulsions are mainly produced and used in industry as substances for consumption or for application to surfaces as carriers for water-insoluble agents. Emulsions are found in cosmetics (lotions, creams, ointments), in cooking (sauces, creams), in pharmaceuticals (ointments, creams), in paint (odour-free paint), in the road industry (emulsified tar), in agrochemicals (phytosanitary products), in detergents, in lamination, iron and steel making and in the production of various deposits (printing, adhesives, etc.).
In cosmetics and pharmaceuticals, for designing hygiene or care products, emulsions constitute an effective method of obtaining a harmonious combination of natural ingredients and different properties in a homogeneous form which is easy to use. The emulsifiers most commonly used at present are alkyl sulphates and sulphonates, alcohols, acids, ethoxylated fatty esters, fatty esters of sorbitan, etc.
Numerous phytosanitary compounds are water-insoluble and, having previously been rendered soluble in an organic solvent, they are capable of being emulsified in water at the time of use or at the moment of formulation with a suitable choice of emulsifiers.
The majority of emulsifiers are found in liquid presentations of phytosanitary products. The emulsifiable concentrate which is the commonest form and still the one most commonly used on the market at present conventionally contains 250 g/l of pesticide, for example, and 50 g/l of emulsifier. It is used by forming a fine emulsion the stability of which has to be ensured for a number of hours irrespective of temperature or the hardness of the water. Concentrated suspensions are a more recent development and correspond to the generation of formulations which allow very low doses to be applied per hectare. This is true, for example, of concentrated emulsions which contain, respectively, 400 to 600 g/l of pesticides and 50 to 100 g/l of emulsifiers. Unlike the two formulations mentioned above, microemulsions are thermodynamically stable systems which are therefore of great interest from the point of view of storage of the products.
The emulsifiers used in the phytosanitary field are essentially when speaking of anionic emulsifiers, calcium dodecyl benzenesulphonate, amine alkylarylsulphonates, ethoxylated fatty esters of alcohol phosphates or ethoxylated alkylphenols. Of the non-ionics, those most commonly used are ethoxylated alkylphenols, alcohols and ethoxylated fatty acids.
The preparation of emulsions using compositions containing polyglycosides and at least one fatty alcohol is well known (WO 92/06778, WO 96/37285, WO 95/13863, WO 98/47610, WO 97/18033, DE 196 07 977).
These emulsifying surfactants may take the form of compositions based on fatty alcohols and polyglycosides which have the advantage of being xe2x80x9cself-emulsifyingxe2x80x9d. The term xe2x80x9cself-emulsifyingxe2x80x9d denotes a composition which can be used to produce an emulsion simply, by mixing with gentle shaking with an aqueous phase.
However, it has been found, particularly in EP 0628305, that the use of such emulsifying compositions did not always result in emulsions which were sufficiently stable over time.
The Applicants have also found that the use of emulsifying compositions according to the prior art did not always result in emulsions which were stable in the presence of silicone oils. However, these oils are valuable because they result in emulsions which are pleasant to touch, giving good penetration and generally water-resistant.
It is therefore proposed according to the present invention to use emulsifiers based on polyglycosides and fatty alcohols to obtain stable emulsions (i.e. which do not separate out after the three months storage at 45xc2x0 C.) even when using less than 5% by weight, based on the total weight of the emulsion, of these emulsifiers, even in the presence of silicone oils.
The high stability of the emulsions has been achieved by using emulsifiers based on fatty alcohol and polyglycosides containing polypentosides selected from among the polyarabinosides, and polyxylosides in specific proportions.
Moreover, the Applicants have found that the emulsions according to the invention, prepared from emulsifier based on fatty alcohol and polyglycosides, had a good suspending power, i.e. they were capable of holding solid particles in suspension, regardless of the viscosity of the emulsion.
In addition, the emulsifiers according to the invention, made up of polyglycosides and fatty alcohols, are of natural origin. They make it possible to prepare stable emulsions of totally plant origin. They do not have the drawbacks of emulsifiers based on polyoxyethylenated compounds which are capable of containing dioxane residues. They are non-irritant, non-toxic and biodegradable.
Moreover, the emulsifiers according to the invention can be used as self-emulsifying compositions.
The present invention thus relates to emulsions containing, by weight:
4.5 to 99.5% of water
0 to 95% of oil
0 to 50% of active substance
an emulsifier making up the total of 100%,
the emulsifier contains 30 to 65% by weight of at least one fatty alcohol of formula ROH, where R is a straight-chained or branched aliphatic radical, which may be saturated or unsaturated, having 1 to 4 ethylenic unsaturations, having 12 to 22 carbon atoms, the remainder consisting, except for impurities, of:
a) either a mixture of polyglycosides comprising polypentosides of formula (I):
R1O(P)n1xe2x80x83xe2x80x83(I)
wherein R1 is a straight-chained or branched, saturated or unsaturated aliphatic radical having 1 to 4 ethylenic unsaturations, with 12 to 22 carbon atoms, P is the residue of a pentose selected from arabinose and xylose, n1 is between 1 and 5; and polyhexosides of formula (II):
R2O(H)2xe2x80x83xe2x80x83(II)
wherein R2 is a straight-chained or branched, saturated or unsaturated aliphatic radical having 1 to 4 ethylenic unsaturations, with 12 to 22 carbon atoms, H is the residue of a hexose, n2 is between 1 and 5;
b) either a mixture of polyglycosides of formula (III):
R3O(G1)a(G2)b(G3)c(G4)d(G5)exe2x80x83xe2x80x83(III)
wherein R3 is a straight-chained or branched, saturated or unsaturated aliphatic radical having 1 to 4 ethylenic unsaturations and 12 to 22 carbon atoms, G1, G2, G3, G4 and G5 independently of one another are residues of an ose selected from among the hexoses and pentoses, the latter being selected from arabinose and xylose; a, b, c, d and e being equal to 0 or 1, the sum of a, b, c, d and e being at least 1
c) or a mixture of a and b
characterised by the following two features 1 and 2:
1) when the emulsifier contains polyglycosides comprising polypentosides of formula (I) and polyhexosides of formula (II), the polypentosides of formula (I) represent 66 to 100% by weight of the total polyglycosides, and the polyhexosides of formula (II) constitute 0 to 34% by weight of the total polyglycosides, when the emulsifier comprises polyglycosides of formula (III), the pentoses then constitute 66 to 100% by weight based on the total oses G1, G2, G3, G4 and G5 and the hexoses constitute from 0 to 34% by weight based on the total oses G1, G2, G3, G4 and G5 and
2-a) either the emulsifier constitutes at least 2.5% of total weight of the emulsion. The oily phase of the emulsion may thus consist of an oil selected from among:
oils of vegetable origin such as sweet almond oil, coconut oil, castor oil, jojoba oil, olive oil, rape seed oil, groundnut oil, hazel nut oil, palm oil, she a tree butter, apricot kernel oil, calophyllum oil, safflower oil, avocado oil, walnut oil, blackcurrant seed oil, wheatgerm oil, sunflower oil, corn seed oil, soya oil, cotton seed oil, alfalfa oil, barley oil, grapeseed oil, poppy oil, pumpkin oil, sesame oil, rye oil, evening primrose oil, passionflower oil, derivatives of these oils such as hydrogenated oils,
oils of animal origin (tallow, fish oils . . . ),
mineral oils such as paraffin oil, vaseline oil and mineral oils obtained particularly from petroleum fractions.
synthetic oils such as poly-xcex1-olefines,
lanolin derivatives,
alkanediols having 2 to 10 carbon atoms such as 1,2-propanediol, 1,3-butanediol,
alcohols of formula R4xe2x80x94OH where R4 is a straight-chained or branched, saturated or unsaturated aliphatic radical having 1 to 4 ethylenic unsaturations and 12 to 22 carbon atoms, such as myristic alcohol, cetyl alcohol, stearyl alcohol and oleic alcohol,
polyethylene glycols or polypropylene glycols,
fatty esters of formula R5xe2x80x94Oxe2x80x94COxe2x80x94R6 wherein R5 and R6 independently of each other denote straight-chained or branched, saturated or unsaturated aliphatic radicals having 1 to 4 ethylenic unsaturations, with 1 to 22 carbon atoms, such as alkyl myristates, particularly butyl myristate, propyl myristate, alkyl palmitates such as isopropyl palmitate, alkyl stearates, particularly hexadecyl stearate, alkyl oleates, particularly dodecyl oleate, alkyl laurates, particularly hexyl laurate, propylene glycol dicaprylate, ethyl-2-hexyl cocoate, esters of lactic acid, behennic acid, isostearic acid such as isostearyl isostearate,
and silicone oils including the cyclic polydimethylsiloxanes, the xcex1-xcfx89-hydroxylated polydimethylsiloxanes, the xcex1-xcfx89-trimethylsilylated polydimethylsiloxanes, the polyorganosiloxanes such as the polyalkylmethylsiloxanes, the polymethylphenyl-siloxanes, the polydiphenylsiloxanes, the amino derivatives of silicones, the silicone waxes, the silicone copolyethers (such as the oil SILBIONE 70646(copyright) sold by RHONE-POULENC or DC 190(copyright) sold by DOW CORNING) or mixed derivatives of silicones such as the mixed copolymers polyalkylmethylsiloxanes-silicones copolyethers.
2-b) or the emulsifier constitutes from 1 to 2.5% of the total weight of the emulsion and the oil is selected from among:
sweet almond oil, coconut oil, castor oil, jojoba oil, olive oil, rape seed oil, groundnut oil, hazelnut oil, palm oil, apricot kernel oil, calophyllum oil, safflower oil, avocado oil, blackcurrant seed oil, sunflower oil, corn seed oil, soya oil, cotton seed oil, alfalfa oil, barley oil, grapeseed oil, poppy oil, pumpkin oil, sesame oil, rye oil, evening primrose oil, passionflower oil, derivatives of these oils, hydrogenated oils,
oils of animal origin (tallow, fish oils . . . ),
synthetic oils, poly-xcex1-olefines,
lanolin derivatives,
alkanediols having 2 to 10 carbon atoms,
alcohols of formula R4xe2x80x94OH where R4 is a straight-chained or branched, saturated or unsaturated aliphatic radical having 1 to 4 ethylenic unsaturations and 12 to 22 carbon atoms,
polyethylene glycols, polypropylene glycols,
the fatty esters of formula R5xe2x80x94Oxe2x80x94R6 wherein R5 and R6 independently of each other denote straight-chained or branched, saturated or unsaturated aliphatic radicals having 1 to 4 ethylenic unsaturations, with 1 to 22 carbon atoms, such as alkyl myristates, particularly butyl myristate, propyl myristate, alkyl palmitates such as isopropyl palmitate, alkyl stearates, particularly hexadecyl stearate, alkyl oleates, particularly dodecyl oleate, alkyl laurates, particularly hexyl laurate, propylene glycol dicaprylate, ethyl-2-hexyl cocoate, esters of lactic acid, behennic acid, isostearic acid such as isostearyl isostearate,
and silicone oils including the cyclic polydimethylsiloxanes, the xcex1-xcfx89-hydroxylated polydimethylsiloxanes, the xcex1-xcfx89-trimethylsilylated polydimethylsiloxanes, the polyorganosiloxanes such as the polyalkylmethylsiloxanes, the polymethylphenyl-siloxanes, the polydiphenylsiloxanes, the amino derivatives of silicones, the silicone waxes, the silicone copolyethers (such as the oil SILBIONE 70646(copyright) sold by RHONE-POULENC or DC 190(copyright) sold by DOW CORNING) or mixed derivatives of silicones such as the mixed copolymers polyalkylmethylsiloxanes-silicones copolyethers.
Generally speaking, when the emulsifier constitutes at least 2.5% of the total weight of the emulsion, emulsions containing 10 to 30% of oil based on the total weight of the emulsion are preferred on account of their pleasant touch.
The emulsions according to the present invention may also contain an emulsifier which complements the emulsifying agent comprising at least one fatty alcohol and a glycoside of the invention, so that the total quantity of emulsifier is less than 25% based on the total weight of the emulsion. However, on account of the great efficacy of the emulsifiers based on fatty alcohol and polyglycosides according to the invention, it is preferable to use as emulsifier only the one according to the present invention.
Generally, the total quantity of emulsifier will be less than 25% of the total weight of the emulsion and will preferably constitute 2.5 to 6% and more particularly 2.5 to 4% of the total weight of the emulsion.
According to an advantageous feature, linked particularly with their excellent stability and good suspending power, emulsions containing emulsifiers based on polyglycosides containing 80 to 100% and more particularly 97 to 100% by weight of polypentosides and 0 to 20% and more particularly 0 to 3% by weight of polyhexosides are preferred.
The term emulsion having a great suspending power denotes an emulsion which is capable of holding in suspension, in well dispersed manner, solid particles having an average size of 50 xcexcm to 500 xcexcm after storage for 3 months at 45xc2x0 C. and centrifugation at 2000 rpm for 3 minutes at 20xc2x0 C.
Each ose group may be in the a or xcex2 isomeric form, in the L or D form and in the furanose or pyranose form. Hexoses of series D are preferred, notably D-glucose, D-galactose and D-mannose. Of the pentoses, L-arabinose and D-xylose are preferred which are found in abundance in the hemicelluloses of numerous plants.
Because of the fact that glucose is abundant on the sugar market, glucosides preferably make up at least 80% of the polyhexosides. For the same reasons, advantageously, the polyxylosides represent 85% and preferably 98% by weight of the polypentosides.
Fatty alcohols of formula ROH having 14 to 22 carbon atoms and notably mixtures of hexadecanol and octadecanol and mixtures of tetradecanol and octadecanol are particularly preferred.
Moreover, on account of their speed of manufacture, the compositions of the invention containing polyglycosides wherein the radicals R1 and R2 or the radical R3 are identical to the radical R of the fatty alcohol are particularly preferred.
On account of their effectiveness and ease of manufacture, emulsifiers containing 40 to 60% by weight of fatty alcohols based on the total weight of emulsifier and preferably 47 to 52% of fatty alcohol, the remainder being polyglycosides, with the exception of any impurities, are most particularly preferred.
The emulsifiers based on polyglycosides and fatty alcohols may be prepared by simply mixing their components together in proportions as specified above. The homogenisation techniques used are those currently used for mixing solid or liquid ingredients. For solid ingredients it is, however, preferable if possible to mix them at a temperature above their melting points in liquid form.
The emulsifiers may be prepared using one of the two methods conventionally used for synthesising alkyl polyglycosides.
The first method consists in directly contacting the reducing sugar and the fatty alcohol in the presence of an acid catalyst to obtain the polyglycosides.
The second method consists, in a first step, of carrying out glycosidation with a short alcohol corresponding to the formula R7OH, where R7 is a C1-5-alkyl radical. In a second step, transglycosidation is carried out, which consists of displacing the short alcohol of formula R7OH with a fatty alcohol.
Each of these two methods may be completed, if required, by operations of neutralisation, filtration, elimination of the excess fatty alcohol and decolorisation.
Advantageously, particularly when using crystalline reducing sugars as starting materials, it is preferable to use the first direct method which has the advantage of being quicker and easy to carry out. However, when reducing sugars in the form of syrups are used, it is preferable to use the second method which produces a more homogeneous reaction medium and consequently polyglycosides of better quality which contain no or very few breakdown products.
The term reducing sugars denotes hexoses, pentoses and the corresponding oligosaccharides having a free anomeric hydroxyl.
During the direct glycosidation of sugars with fatty alcohol or a mixture of fatty alcohols, or during transglycosidation if the grafting is carried out in two steps, the fatty alcohol is preferably used in excess (1 to 3 and preferably 1.5 to 2.5 molar equivalents based on the reducing sugars), so that the reaction product contains the quantities of free fatty alcohol and polyglycosides specified hereinbefore.
It would also be possible to eliminate the fatty alcohol or mixture of fatty alcohols totally or partially at the end of the synthesis and then add specified proportions of a fatty alcohol or a mixture of fatty alcohols which is different or identical to those used during synthesis in order to obtain the emulsifier according to the invention.
However, the first solution is preferred, which consists in using the excess fatty alcohol so that the reaction product contains the specified amounts of fatty alcohols and polyglycosides.
In practice, there are three main methods of obtaining the emulsifiers according to the invention from reducing sugars and fatty alcohols.
The first method consists in carrying out the glycosidation of the reducing sugars separately (hexoses such as glucose, galactose, mannose and the corresponding oligosaccharides, pentoses selected from among arabinose and xylose and the corresponding oligosaccharides) by contacting them with one or more fatty alcohols in the presence of an acid catalyst conventionally used for reactions of glycosylation. It is preferable to use the fatty alcohol in excess (1 to 3 and preferably 1.5 to 2.5 molar equivalents based on the reducing sugars) so that the reaction product contains the specified amounts of free fatty alcohol and polyglycosides. After neutralisation of the acid catalyst, the polypentosides of formula (I):
R1O(P)n1xe2x80x83xe2x80x83(I)
and the polyhexosides of formula (II) are obtained:
R2O(H)n2xe2x80x83xe2x80x83(II).
Then, 66 to 100%, advantageously 80 to 100% and preferably 97 to 100% by weight of polypentosides, based on the total weight of polyglycosides, and 0 to 34%, advantageously 0 to 20% and preferably 0 to 3% by weight of polyhexosides, based on the total weight of the polyglycosides, are mixed in the presence of fatty alcohol of formula ROH, if necessary, in order to obtain the emulsifiers according to the invention.
The second method comprises mixing 66 to 100%, advantageously 80 to 100% and preferably 97 to 100% by weight of pentoses and/or the corresponding oligosaccharides, based on the total weight of reducing sugars, with 0 to 34%, advantageously 0 to 20% and preferably 0 to 3% by weight, based on the total weight of reducing sugars, of hexoses and/or the corresponding oligosaccharides and carrying out glycosidation of the mixture of reducing sugars thus obtained. The glycosylation is carried out in the presence of an acid catalyst with an excess (1 to 3 and preferably 1.5 to 2.5 molar equivalents in relation to the reducing sugars) of fatty alcohol so that the reaction product preferably contains the specified amounts of free fatty alcohols. The reaction product is neutralised and if necessary the fatty alcohol of formula ROH is added in order to obtain the specifications given above.
Finally, the third method consists in using syrups of mixtures of the reducing sugars derived from raw plant materials rich in starch and hemicellulose containing 66 to 100%, preferably 80 to 100% and more particularly 97 to 100% of pentoses and 0 to 34%, preferably 0 to 20% and more particularly 0 to 3% of hexoses and carrying out glycosidation of these syrups of reducing sugars with fatty alcohols in order to obtain the emulsifiers according to the invention.
According to an advantageous feature of the invention, connected in particular with the ease of industrial synthesis, the very great reactivity of pentoses compared with glucose during the reaction of glycosylation (cf. WO 9729115) and the natural abundance of D-xylose, particularly preferred emulsions are those containing an emulsifier prepared by bringing crystalline D-xylose into direct contact with 1 to 3 and preferably 1.5 to 2.5 molar equivalents, based on xylose, fatty alcohol or a mixture of fatty alcohols of formula ROH, so that the reaction product contains the quantities of fatty alcohol and polyglycosides specified hereinbefore, in the presence of an acid catalyst such as sulphuric acid, a sulphonic acid such as methanesulphonic acid, hydrochloric acid, hypophosphorous acid or any other acid catalyst for carrying out glycosidation and mixtures thereof, at a temperature of between 50 and 100xc2x0 C. and preferably between 80 and 90xc2x0 C. The acid catalyst is then neutralised. Neutralisation is carried out, for example, using an alkali metal or alkaline earth metal hydrogen carbonate or carbonate, notably sodium hydrogen carbonate, an alkali metal or alkaline earth metal hydroxide, notably sodium hydroxide, or an organic base such as triethanolamine. If required, the insoluble matter can then be filtered off or some or all of the free fatty acid may be evaporated. The emulsifier obtained is colourless and free from breakdown products. At the end of the synthesis, depending on the fatty alcohol or mixture of fatty alcohols used, it takes the form of a solid, paste-like or liquid wax. Starting from a solid wax it is possible to obtain powder, flakes or beads or pastilles, particularly for ease of use at a later stage. It is preferable to isolate the composition in the form of hemispherical pastilles about 2 mm in diameter and 0.7 mm thick, which are very easy to use thereafter, notably for the production of emulsions.
Of course, the emulsions according to the invention comprising an emulsifier containing at least one fatty alcohol and polyglycosides may also contain 0 to 50% of one or more active substances such as conventional cosmetic, lipophilic or hydrophilic adjuvants, especially those which are already currently used in the manufacture and production of emulsions. Of the conventional cosmetic adjuvants which may be contained in the aqueous phase and/or fatty phase of the emulsions, the following may be mentioned in particular:
ionic or non-ionic thickeners and gelatinising agents such as cellulose derivatives (carboxymethylcellulose, hydroxyethylcellulose), guar (hydroxypropylguar, carboxymethylguar, carboxymethylhydroxypropylguar), carob, tree exsudates (gum arabic, karaya), seaweed extracts (alginates, carrageenates), exudates of microorganisms (xanthane gum),
hydrotropic agents such as short C2-8-alcohols, particularly ethanol, diols and glycols such as diethyleneglycol, dipropyleneglycol, etc.
hydrating agents (or skin moisturisers such as glycerol, sorbitol, collagen, gelatin, aloe vera, hyaluronic acid, urea or skin protecting agents such as proteins or protein hydrolysates, cationic polymers such as cationic derivatives of guar (JAGUAR C13S(copyright), JAGUAR C162(copyright), HICARE 1000(copyright) marketed by RHONE-POULENC),
glycolipids such as lipid sophoroses,
mineral powders or particles such as calcium carbonate, mineral oxides in the form of powder or in colloidal form (particles smaller than or of the order of one micron, sometimes several tens of nanometres) such as titanium dioxide, silica, aluminium salts generally used as anti-perspirants, kaolin, talc, clays and derivatives thereof, . . .
preservatives, such as the methyl, ethyl, propyl and butyl esters of p-hydroxybenzoic acid, sodium benzoate, GERMABEN(copyright) or any other chemical agent which prevents bacterial proliferation or mould and is traditionally used in cosmetic compositions, are generally added to these compositions in amounts of 0.01 to 3% by weight.
Instead of these chemical agents it is sometimes possible to use agents which modify the activity of water and greatly increase the osmotic pressure, such as carbohydrates or salts.
organic sun filters which are active in UV-A and/or UV-B for protecting the skin or hair from the effects of the sun and UV radiation, such as the compounds authorised in European Directive No. 76/768/EEC, the annexes thereto and subsequent amendments to this directive,
photoprotective mineral monopigments such as titanium dioxide or cerium oxides in the form of powder or colloidal particles.
softeners, antioxidants, self-tanning agents such as DHA, insect repellant agents, vitamins, perfumes, fillers, sequestering agents, dyes, buffers, etc.
abrasives such as ground apricot kernels, micro-beads, . . .
The emulsions prepared from the emulsifier according to the invention may be used in various cosmetic or dermatological applications, for example in the form of creams for the face, body, scalp or hair or in the form of body lotions or makeup removing lotions or in the form of ointments for pharmaceutical use, for example. These emulsions may also be used for makeup, notably in the form of foundations after the addition of pigments. They may also be used as sun creams after the addition of UVA and/or UVB and/or DHA filters or as after-sun creams or lotions after the addition of soothing compounds such as panthenol.
The emulsions may also contain ionic or non-ionic surfactants with a washing, foaming or detergent action such as sodium laurylether sulphate, alkyl betaines, APGs, for producing washing emulsions such as moisturising washing creams or emulsions for shaving.
The emulsions may also contain, with a view to improving their cosmetic qualities, a cosmetic wax such as rice wax, candellila wax or Japan wax. The proportion of wax is generally between 0.5 and 3%, preferably between 1 and 2% by weight, based on the total weight of the emulsion.
The emulsifying agents based on polyglycosides and fatty alcohols according to the invention may also be used in formulations where finely divided solids have to be kept suspended in water, e.g. formulations of agrochemical active substances (herbicides, insecticides, fungicides, etc.) known under the generic title of xe2x80x9cconcentrated suspensionsxe2x80x9d. Apart from a dispersant or emulsifier used in an amount from 1 to 50 g/l, the additives found in a concentrated suspension formulation are additives such as those described in the commercial brochure xe2x80x9cAuxiliaries for agrochemical formulationsxe2x80x9d edited by RHONE-POULENC GERONAZZO SpA. One might mention, for example, a wetting surfactant chosen from among the alkyl derivatives of aryl aliphatic alcohols, the aryl sulphonate derivatives such as sodium isopropylnaphthalene sulphonate marketed under the name SUPRAGIL WP(copyright) by RHONE-POULENC GERONAZZO, the dialkylsulphosuccinates such as sodium di-ethyl-2 hexylsulphosuccinate, dispersant polymers such as polyacrylic acids and the salts thereof, copolymers of maleic anhydride (or acid) and diisobutylene and the salts thereof such as GEROPON T36(copyright) (RHONE-POULENC GERONAZZO), the condensed sodium methyl naphthalenesulphonates such as SUPRAGIL MNS90(copyright) (RHONE-POULENC GERONAZZO), the dispersant polymers derived from lignin such as sodium lignosulphonates or calcium lignosulphonates or other dispersant surfactants such as alkoxylated, optionally sulphated or phosphated derivatives of tristyrylphenols. These formulations may also contain anti-freeze additives such as propylene glycol and thickeners which modify the rheological behaviour of the suspension, such as xanthane gum, cellulose derivatives (carboxymethylcellulose), guar gum or derivatives thereof, clays or modified clays such as bentonite and bentones. Of the active substances which may be formulated in this way, those generally used have a melting point greater than 45xc2x0 C., preferably above 60xc2x0 C. with a water solubility of less than 10 g/l, preferably less than 1 g/l. The active substances for plant protection involved here are herbicides, fungicides and insecticides such as those described in THE PESTICIDE MANUAL (9th Edition, C. R. WORKLING and R. J. HANCE, editors, published by The British Crop Protection Council) which meet the criteria described above.
The emulsifiers based on polyglycosides and fatty alcohols according to the invention may also be used in plant-protection formulations such as emulsifiable concentrates, concentrated suspensions, concentrated emulsions, microemulsions or suspo-emulsions. They are used in concentrations of between 5 and 150 g/l. The active plant-protecting substances may be those described hereinbefore for concentrated suspensions. The emulsifiers of the present invention are particularly effective for preparing plant protecting concentrated emulsions. The active substance is suspended in water using the emulsifier, which ensures the stability of the concentrate during storage as well as the spontaneity and stability of the diluted emulsion when it is used. Typical compositions are made up of about 40 to 80% of active substance, such as for example fatty acid esters such as methylesters of rape seed (EMC) marketed by Robbe and 1 to 15% of additives. This form provides ease of use of the emulsifiable concentrates, with the major advantage of an aqueous carrier instead of a solvent, which provides greater safety.
The emulsifying agents according to the present invention are also effective in the preparation of gas oil emulsions used as diesel fuel. They allow water to be incorporated in the fuel, thereby reducing the omissions of toxic combustion gases. These emulsions are generally made up to 60 to 97% of gas oil, 2.5 to 39.5% of water and 0.5 to 5% of emulsifier. They may also contain the additives currently used in diesel-type fuels.
Four main methods of producing emulsions are proposed:
The first consists in heating all the ingredients at the same time to a temperature of between 50 and 90xc2x0 C. and particularly between 70 and 75xc2x0 C., then homogenising with a blade-type rotary stirrer rotating at 500 to 15000 rpm, particularly at 1000 to 2000 rpm, at a temperature of between 50 and 90xc2x0 C., and then cooling, with gentle stirring (from 100 to 1000, particularly from 300 to 500 rpm) down to a temperature of the order of 25xc2x0 C. If homogenisation is lively when heated, it is not always advisable to stir the emulsion during cooling.
The second consists in working by phase inversion. In this case, the lipophilic and hydrophilic phases are heated separately to a temperature of between 50 and 90xc2x0 C. The lipophilic phase, which contains the composition according to the invention, is stirred vigorously with a blade-type rotary stirrer rotating at 500 to 15000 rpm, particularly 1000 to 2000 rpm, and the hydrophilic phase is slowly added to this phase at a rate such that the hydrophilic phase is instantly absorbed by the lipophilic phase, until phase inversion occurs, characterised by an abrupt change in viscosity. The addition may then be carried out more rapidly at a rate such that the hydrophilic phase stagnates for 1 to 3 seconds above the lipophilic phase if it is being added from above. The emulsion is then left to cool with gentle stirring (100 to 1000, particularly 300 to 500 rpm) down to a temperature of the order of 25xc2x0 C.
The third method is carried out by dispersion. In this case, the lipophilic phase (which contains the emulsifier according to the invention) and the hydrophilic phase are heated separately to a temperature of between 50 and 90xc2x0 C. and preferably to between 70 and 75xc2x0 C. The hydrophilic phase is stirred with a blade-type rotary stirrer rotating at 500 to 15000 rpm, particularly 1000 to 2000 rpm, and the lipophilic phase is progressively added thereto at a rate such that the lipophilic phase is instantly absorbed by the hydrophilic phase. The emulsion is then left to cool with gentle stirring (at 100 to 1000, particularly 300 to 500 rpm) down to a temperature of the order of 25xc2x0 C.
The fourth method consists in heating all the ingredients at the same time to a temperature between 50 and 90xc2x0 C., then homogenising them with a blade-type rotary agitator rotating at 100 to 1000 rpm and passing the resulting mixture through a xe2x80x9chigh pressurexe2x80x9d homogeniser once or a number of times. xe2x80x9cHigh pressurexe2x80x9d homogenisers are apparatus which allow the mixture being emulsified to be subjected to pressures ranging from 10 to 1000 bar and particularly 50 to 500 bar.
According to another aspect of the invention, the composition based on polyglycosides may be used as a self-emulsifying base for the preparation of emulsions by hot dispersion of the compositions according to the invention, e.g. at about 50 to 90xc2x0 C., in water or a suitable polar medium, by simple agitation, notably mechanical or by sonication. If the composition is dispersed in water by agitation or by sonication at a temperature close to the melting point of the emulsifier, dispersions rich in vesicles are obtained.
The two main evaluation criteria which demonstrate the good stability of the emulsions obtained with the 30 emulsifiers according to the present invention are as follows:
The resistance to centrifugation by determining the foaming index, which is defined as the percentage by volume of residual foamed emulsion after a treatment of destabilisation by centrifugation at 4080 g for 1 hour at 25xc2x0 C. The more extreme the percentage of foamed emulsion, the better the result. After centrifugation, the foaming index is the ratio of the volume of residual emulsion over the total volume of initial emulsion multiplied by 100.
Monitoring the retrodiffusion of the emulsions by means of a vertical scanning macroscopic analyser such as the xe2x80x9cTURBISCAN 2000xe2x80x9d. In fact, the instability of the emulsions is often the result of a combination of physical processes implying two main types of phenomena, in particular:
An increase in the size of the droplets or aggregates (coalescence, flocculation).
The migration of the droplets into the sample (foaming, sedimentation).
The foaming and sedimentation are sometimes regarded as harmless phenomena whereas coalescence is always disastrous for the formulator on account of being irreversible. It therefore appears to be important to detect these phenomena at a very early stage (to reduce the ageing tests which are at least 90 days at 45xc2x0 C.) and identify them. The method of evaluating the stability of the emulsions proposed here makes it possible to detect local variations in the concentrations and/or sizes of the particles in a concentrated medium well before the naked eye can. This technique also allows us to obtain information as to the type or types of physical processes involved in the destabilisation of the mixture and the order of their appearance. The most stable emulsions are those which have the smallest variation in retrodiffusion as a function of time.
In order to evaluate the good suspending power of the emulsions according to the present invention, we have prepared them by adding, as additives, solid particles ranging in size from 0.05 to 0.250 mm. We then subjected the emulsions to a destabilising treatment by centrifuging at 2000 rpm for 3 minutes at 20xc2x0 C. We then measured the deposit of solid particles left at the bottom of the tube. The results are expressed as a percentage of the deposit defined by the volume of the deposit in relation to the total volume of emulsion centrifuged. The emulsions having the best suspending powers are those for which we do not obtain any deposit at all.